Lisa Pour was 40 when she vanished on January 16 2013 – after last being seen by a probation officer in the Willesden Green area of north-west London.
Enquiries into the mother-of-three over the past 10 years failed to find out what happened to her and detectives now believe she is dead.
The investigation has been passed to murder detectives from the Metropolitan Police’s Specialist Crime Command.
Ms Pour was staying at a flat in Kilburn High Road when she disappeared but was known to frequent Camden and Brent and be popular with drug takers.
In January, her family offered a £10,000 reward to anyone coming forward with significant information.
Detective Chief Inspector Neil Rawlinson of the Met’s Specialist Crime Command said: “Lisa was a mother of three children that she adored, she was close to her parents and while her lifestyle could be described as somewhat chaotic, she would not have broken contact with her loved ones.”
Reza Pour, Ms Pour’s father, said: “Lisa’s absence in our lives has been a daily struggle but we always held on to the hope that she might still come back to us.
“To think that her last moments may have been filled with fear and pain is something that we cannot get over. Someone out there knows what happened to our beloved Lisa.
“Please come forward and help us find justice for her and find her body so she can properly be laid to rest.”
Ms Pour was about 5ft 2ins tall and of slim build with dark hair.
Anyone with information can call the incident room on 020 8358 0200, call 101 or Tweet @MetCC, or call the independent charity Crimestoppers anonymously on 0800 555 111.